Excess variance in the E = 3 − 79 keV energy band versus the black hole mass of the AGN (left). The excess variances shown here are averaged among the different epochs. A clear trend ${\sigma }_{\mathrm{NXS}}^2\propto M_{\mathrm{BH}}^{-0.6}$ is found with a strong anticorrelation (r = −0.7). Given their large uncertainties, masses obtained with the velocity dispersion method (red diamonds) are excluded from the fit. Middle panel gives The average excess variance vs. the unabsorbed X-ray luminosity L_X is shown. We find a trend ${\sigma }_{\mathrm{NXS}}^2\propto L_{\mathrm{X}}^{-0.4}$ with moderate anticorrelation (r = −0.5). Right panel shows the average excess variance vs. the Eddington ratio and no evident correlation is found. Also, in this panel, the sources with mass measurements obtained with the velocity dispersion method are drawn as red diamonds.